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4
Access control
4.1
PurposeUndercertain circumstances, it will be desirable to prevent UE users from makingaccess attempts (including emergency call attempts) or responding to pages inspecified areas of a
PLMN. Suchsituations may arise during states of emergency, or where 1 of 2 or moreco-located PLMNs has failed.
Broadcast messages should be available on acell by cell basis indicating the class(es) of subscribers barred from networkaccess.
The use of this facility allows the networkoperator to prevent overload of the access channel under critical conditions.
It is not intended that access control beused under normal operating conditions.
4.2
Allocation
All UEs are members of one out of ten randomly allocated mobilepopulations, defined as Access Classes 0 to 9. The population number is storedin the SIM/USIM. In addition, mobiles may be members of one or more out of 5special categories (Access Classes 11 to 15), also held in the SIM/USIM. Theseare allocated to specific high priority users as follows. (The enumeration isnot meant as a priority sequence):
Class
15
-
PLMN Staff;
-"-
14
-
Emergency Services;
-"-
13
-
Public Utilities (e.g. water/gassuppliers);
-"-
12
-
Security Services;
-"-
11
-
For PLMN Use.
4.3
OperationIf the UE is a member of at least one Access Class which correspondsto the permitted classes as signalled over the air interface, and the AccessClass is applicable in the serving network, access attempts are allowed.Otherwise access attempts are not allowed.
Access Classes are applicable as follows:
Classes 0 - 9
-
Homeand Visited PLMNs;
Classes 11 and 15
-
Home PLMN only;
Classes 12, 13, 14
-
Home PLMN and visitedPLMNs of home country only.
Any number of these classes may be barred at any one time.
4.4
Emergency CallsAn additional control bit known as"Access Class 10" is also signalled over the air interface to the UE.This indicates whether or not network access for Emergency Calls is allowed forUEs with access classes 0 to 9 or without an IMSI. For UEs with access classes11 to 15, Emergency Calls are not allowed if both "Access class 10"and the relevant Access Class (11 to 15) are barred. Otherwise, Emergency Callsare allowed.